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Matthew
H. Davis and Ingrid S. Johnsrude (2003)

Hierarchical
Processing in Spoken Language Comprehension

The Journal of
Neuroscience, 23(8), p.3423-3431

Stimuli:

Three forms of
distorted, yet intelligible speech were used in the study. The three forms of
distortion (and normal speech) are shown in the spectrograms below.

Click on the
spectrogram to hear an example sentence in each form of distortion (and as normal
speech):

The distorted
example sentences above are all of medium intelligibility. For each form of
distortion, three levels of intelligibility were constructed: low intelligibility
(~20% words reported correctly from each sentence), medium intelligibility (~65%
words reported correctly), high intelligibility (~90% words reported correctly).
The intelligibility of each form of distortion was assessed from a pilot behaviuoral
study in which participants had to either type the words heard in each sentence
or give a 9 point rating of intelligibility. In both the pilot study and the
fMRI study, report scores and subjective ratings were closely correlated.

In the graph
below, you can click on a data point to play an example speech sound with that
type and level of distortion.

Or click the
speaker in the table below:

Segmented
Speech

Vocoded
Speech

Speech
in Noise

Normal
Speech

High
Intelligibility

Medium
Intelligibility

Low
Intelligibility

Signal
Correlated Noise

All the speech
distortions were created using Praat software
with assistance from Paul Boersma and Chris Darwin. If you would like to find
out more about any of the three forms of distortion please contact matt.davis@mrc-cbu.cam.ac.uk.